Add SPDX annotation

Related: OS#3515
Change-Id: I3719bd8dc015569ecd81928fc079e27593cdca09
diff --git a/Transceiver52M/osmo-trx.cpp b/Transceiver52M/osmo-trx.cpp
index 8a3f1e3..cd659a7 100644
--- a/Transceiver52M/osmo-trx.cpp
+++ b/Transceiver52M/osmo-trx.cpp
@@ -1,6 +1,8 @@
 /*
  * Copyright (C) 2013 Thomas Tsou <tom@tsou.cc>
  *
+ * SPDX-License-Identifier: LGPL-2.1+
+ *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either